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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 5 (1997), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Oyster cultch was added to the lower intertidal fringe of three created Spartina alterniflora marshes to examine its value in protecting the marsh from erosion. Twelve 5-m-wide plots were established at each site, with six randomly selected plots unaltered (non-cultched) and cultch added to the remaining (cultched) plots. Within each cultched plot, cultch was placed along the low tide fringe of the marsh during July 1992, in a band 1.5 m wide by 0.25 m deep. Marsh-edge vegetation stability and sediment erosion were measured for each plot from September 1992 to April 1994. Significant differences (p 〈 0.05) in marsh-edge vegetation change were detected at the only south-facing site after a major southwester storm. Significantly different rates of sediment erosion and accretion also were observed at this same site. Areas upland of the marsh edge in the cultched areas showed an average accretion of 6.3 cm, while noncultched treatment areas showed an average loss of 3.2 cm. A second site, with a northern orientation, also experienced differential sediment accretion and erosion between treatment type, caused instead by boat wakes that were magnified by the abutment of a dredge effluent pipe across the entire front fringe of the site. During this period we observed significant differences in sediment accumulation, with the areas upland of the marsh edge in the cultched treatment having an average accretion of 2.9 cm and the noncultched an average loss of 1.3 cm.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was undertaken to evaluate the interrelationship between the presence of seagrasses, Zostera marina and Halodule wrightii, and the physical and chemical properties of sediments in a coastal plain estuary near Beaufort, North Carolina. In sediments underlying a cover of seagrass, silt-clay, organic matter, exchangeable ammonium, ammonium dissolved in pore waters and total nitrogen were larger than in unvegetated profiles. The magnitude of the physical and chemical properties of sediments varied according to the location of the station in relation to the vegetation, as well as the continuity in the distribution of the seagrass. The largest pools of nitrogen, the finest sediment texture, and the greatest organic matter content were in sediments associated with the mid bed regions of seagrass meadows, intermediate at the edges of the bed and small isolated patches of grass, and least in unvegetated substrate. General conclusions from this study are: 1) once established, seagrasses appear capable of modifying the sediment texture as well as the organic matter and nitrogen content; 2) nitrogen accumulates beneath the vegetation suggesting that vegetated sediments are sinks; however, functional recycling mechanisms seem to be operating as suggested by the larger magnitude of remineralized nitrogen in the vegetated profiles; and 3) the establishment of seagrasses in this geographical region are not necessarily restricted by the sediment properties measured in this study. These data and conclusions are discussed in regard to an application of contemporary theories of ecosystem development to seagrass systems.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Inorganic nutrients limiting phytoplankton production in the shallow estuarine system near Beaufort, N. C., were identified by nutrient enrichment techniques. Nitrogen was the primary limiting nutrient; phosphorus also was limiting at times. Samples receiving a complete enrichment medium plus organic substrates poor or lacking in nitrogen and phosphorus showed no significant increase in relative photosynthesis over unenriched controls, even though there was a significant decrease in the nitrogen and phosphorus concentrations in the enriched samples. This suggested that microbial immobilization of nitrogen and phosphorus during decomposition of organic matter may limit nutrient availability to phytoplankton and in part account for the general paucity of inorganic nutrients present in this shallow system. An estimated 6 x 109 g carbon, 1 x 108 g nitrogen and 2 x 107 g phosphorus enters the estuarine system in the form of partially decayedSpartina alterniflora each year, primarily from September–March. To utilize the readily available fraction of this detrital material estuarine microbes would have to immobilize 2.4 x 107 g nitrogen and 1.6 x 106 g phosphorus. The data also suggested that an annual cycle in nutrient concentration in the estuarine system in part may result from shifts in the equilibrium between microbial immobilization and remineralization.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Living and dead Zostera marina blades, plankton samples, sediments, and several animal components of an eelgrass bed near Beaufort, N.C. were collected and analyzed for 13C/12C ratios (δ 13C). The δ 13C values of producer and consumer organisms were compared in order to examine the possible origins of organic matter present in the consumers. Living and dead eelgrass blades displayed similar δ13C values,-12.2 and-10.6 per mil ‰ respectively, while the epiphytic community growing on the grass blades had a mean isotope ratio of-16.0‰. Animal components analyzed represented five major feeding-mode categories: invertebrates living on grass blades an presumably feeding on the epibiota (-15.1‰), deposit feeding invertebrates (-15.0‰), predatory and omnivorous invertebrates (-16.7‰), suspension and surface feeding invertebrates (-18.3‰) and omnivorous fish (-16.8‰). Organisms commonly found on the grass blades appeared to feed primarily on the epibiota growing on the blades. It is hypothesized that the epibiota derive some of their carbon from DOC released by the Zostera blade. The urchin, Lytechinus variegatus, and the brittle star, Ophioderma brevispinum, both deposit feeders, appeared to derive a major proportion of their carbon from eelgrass. With the exception of the shrimp, Alpheus heterochaelis, and the pipefish, Syngnathus floridae, the majority of other organisms analyzed appeared to be linked more directly to a plankton-carbon food chanin than to a seagrass-carbon system in this relatively young eelgrass bed.
    Type of Medium: Electronic Resource
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